The major cause of reduction in wafer fabrication yield in the pre-process of semiconductor manufacturing has conventionally been a foreign matter appearing randomly on a semiconductor wafer, and the yield has been maintained by reducing foreign matters. However, in recent years, the minimum pattern line widths of semiconductor devices have been decreasing from 45 nm to 32 nm, and the proportion of design-layout-dependent defects is increasing.
Such a layout-dependent defect is called a systematic defect. Examples of a systematic defect include an abnormality in resistance caused by a variation in pattern shape resulting from a difference in level of an underlayer and faulty electrical continuity of a contact hole caused by insufficient etching at a specific region of a gate oxide film.
In order to reduce defects in semiconductor wafers, a semiconductor wafer is inspected by, e.g., a dark-field, bright-field, or electron-beam defect inspecting apparatus during the manufacture of the semiconductor wafer. A review apparatus acquires clear images of defects on the basis of information on the positions of the defects detected by any of the inspecting apparatuses. ADC (Automatic Defect Classification) that refers to automatically classifying a defect is performed on the basis of the images. Measures are taken against defects according to categories, into which defects are classified, and the frequency of defects.
However, the conventional ADC classification remains within classification into categories based on the shape, brightness, and the like of a defect observed with a review apparatus and cannot identify the cause of a layout-induced systematic defect. Accordingly, there has recently been a need for a technique for classifying a defect using design layout data.
Methods for checking a defect against design layout data have already been reported. Patent Literature 1 below discloses the process of superimposing a defective image on layout data and determining, on the basis of the position of a defect, information on the density of defects in a region, and the like, whether the defect is a systematic defect, in order to identify the cause of a defect.